Method for recovering hydroxy-3-etiocholenic acid and its esters



Patented Aug. 1, 1944 v E'rIoono Emojncme n ITS ESTERS Rupert" Oppn'auen Amsterdani,'- and Carel ,1 Christof Bolt,-, 055; Netherlands, assignors to v 4 w Jer Roche Organon Inc.,;l Iutley,-N. 3., a corpora- Nonra ing. Application February 6,1940, Serial e No. 317,608 In the Netherlands March 16, 1939 1'0 ciaihisl (omen-397.1)

I -'Thi s "invention relates to a' p r'ocess' for' recov ering hydroxy f3 etio'choleni c"acid and'it's esters from mixtureswith hoiiiologous acids: The hydroxy-3-etiocholenic acid, an important intermediate product-"iri'-the preparation of substances showing 'a-h'orr'i'ione action, has been" 'prepared for th'ej'first tim'ebyj decompositionof hydroxy-3 -bisnorc'holenic acid {of coperiding appli cation by Rupert"O'ppenauer, Ser."No'. 195,158; filed March" l0, 1938). iThisfst artmgjmaterial', however, "is; rather expensive. In the Search for another'st'arting material it appeared'that the hydroxy-3-etiocholenic acid also occurs in the acid reaction products formed by' the oxidation of sterols, e. g., cholesterol; with, chromicacid', though the British specification' No. 453,773 does not mention the hydroxy-3-etiocholenic acid'as a component of'the homologous acids occurring in the acid oxidation products.

It nowfhas been found that it' isfp'ossible to recover the desired etiof'acid from fthemixture so obtained in a'surprisingly s'imple'fmanner by subjecting 'the esters ofthese acids, preferably the methylesters, to a'dire'ct fractional crystallisation. If desired, a preliminary purification may be carried out utilising the fact that some of the acids contained in the crude mixture among which is found the hydroxy-3-etiocholenic acid, form a difficultly soluble sodium salt. For carrying out the present method, however, this preliminary purification is not essential.

We have further found that the esters of hydroxy-3-etiocholenic acid, and particularly the methyl esters, have a substantially lower solubility in organic solvents than the esters of the other acids. This difference in solubility appears very distinctly in solvents consisting entirely or partly of hydrocarbons. Particularly suitable are mixtures of aliphatic and aromatic hydrocarbons. As aliphatic hydrocarbons the pure hydrocarbons, such as pentane, hexane and the like, may be used, but the cheaper petroleum ether consisting of a mixture of such hydrocarbons is also suitable. From the aromatic hydrocarbons benzene and toluene may be mentioned as an example.

The ester fraction obtained by the first crystallisation is already rather pure hydroxy-B- etiocholenic acid ester; by recrystallising a number of times from the same solvent the substance is easily obtained in pure condition.

The esters may be prepared in the usual manner, e. g., by boiling with the desired alcohol in presence of sulphuric acid, aromatic sulphonic acids such as toluene sulphonic' acid, and the like. The neutral esters are then freed from acids remained unesterified and/or acid esters by'means of alkali, after which they are subjected to the crystallisation as above described. The estersused in the examples are obtained by the oxidation of cholesterol; the method may, however, be carried out with equally good results with the acids obtained by the oxidation of other sterols. The'pure esters obtained may subsequently be converted into the corresponding acids by saponification. Example 1.The acids obtained from the insoluble sodium salts were esterified with methanol under the influence of sulphuric acid. The esters obtained'in this manner were freed from the acid components, e. g., by extraction with carbon tetrachloride from an aqueous alkaline medium, the acid components remaining in the aqueous medium.

620 g. of the methyl esters obtained in that mar'ineewere dissolved in 1200 cm. of benzene after'which 600 cm. of petroleum ether (B. P. 40-60 C.) were added. The mixture was allowed to stand some days at room temperature, whereupon the precipitate formed was filtered off with suction and recrystallised a number of times from a mixture consisting of 2 parts of benzene and 1 part of petroleum ether. In this manner 17 g. of hydroxy-3-etiocholenic acid methyl ester having a melting point of 1'78-180 C. was obtained which appeared to be identical with the methyl ester of hydroxy-3-etiocholem'c acid obtained by decomposition of hydroxy-3-bisnorcholenic acid.

Example 2.-5 g. of still impure hydroxy-3- etiocholenic acid methyl ester were dissolved in cm. of toluene and 100 cm. of petroleum ether. After keeping 2 days in the refrigerator 4 g. of pure ester having a melting point of 178- 180 C. could be recovered.

Example 3.750 g. of crude methyl esters were dissolved in a mixture of 700 cm. of toluene and 250 cm. of petroleum ether. After some days the precipitate which had formed, and which weighed 41.7 g., was recovered. From this precipitate 30 g. of pure hydroxy-3-etiocholenic acid methyl ester having a melting point of 1'78-180 C. were obtained by recrystallising twice from a mixture of toluene and petroleum ether.

Example 4.620 g. of crude methyl esters were dissolved in a mixture of 1000 cm. of benzene and 350 cm. of petroleum ether (B. P. 40-60 C.). After being kept 3 days at room temperature the precipitate weighing 80 g. was recovered by filtration with suction and recrystallised twice from 1. A method for recovering hydroxy-3-etiocholenic acid and its esters from mixtures with homologous acids, comprising esterification of the mixture of acids, fractional crystallisation from a solvent containing essentially at least one hydrocarbon and recovery of the hydroxy-S-tiocholenic acid ester from the first crystal fractions.

2. A method for recovering hydroxy-B-etiocholenic acid and its esters from mixtures with homologous acids, comprising conversion of the mixture of acids into the methyl esters, frac-' tional crystallisation from a solvent containing essentially at least one hydrocarbon and recovery of the hydroxy-3-etiocholenic acid methyl ester from the first crystal fractions.

3. A method for recovering hydroxy-3-etiocholenic acid and its esters from'mixtures with homologous acids, comprising esterification of the mixture of acids, fractional crystallisation from a solvent containing essentially a mixture of hydrocarbons and recovery of the hydroxy-3-etiocholenic acid ester from the first crystal fractions.

4. A method for recovering hydroxy-B-etiocholenic acid andits esters from mixtures with homologous acids, comprising esterification of the mixture of acids,. fractional crystallisation from a solvent consisting of a mixture of benzene and a low boiling petroleum ether and recovery of the hydroxy-3-etiocholenic acid ester from the first crystal fractions. 1

5. A method for recovering hydroxy-B-etiocholenic acid and its esters from mixtures with homologous acids; comprising conversion of the mixture of acids into the methyl esters, fractional cholenic acid and its esters comprising the steps of oxidation of sterols to obtain a resultant mix ture of acids, esterification of said mixture of acids, fractional crystallization from a solvent containing essentially at least one hydrocarbon, and recovery of the hydroxy-Zi-etiocholenic acid ester from the first crystal fractions.

8. A method for obtaining hydroxy-3-etiocholenic acid and its esters comprising the steps of oxidation of sterols to obtain a resultant mixture of acids, conversion of said-mixture of acids into the methyl esters, fractional crystallization from a solvent containing essentially at least one hydrocarbon, and recovery of the hydroxy-3-etiocholenic acid methyl ester from the first crystal fractions.

9. A method for obtaining hydroxY-B-etiocholenic acid and its esters comprising the steps of oxidation of sterols to obtain a resultant mixture of acids, esterification of said mixture of acids, fractional. crystallization from a solvent consisting of a mixture of benzene and a low boil ing petroleum ether, and recovery of the hydroxy- 3-etiocholenic acid ester from the first crystal fractions.

10. A method for obtaining hydroxy-3-etiocholenic acid and its esters, comprising the steps of oxidation of sterols to obtain a resultant mixture of acids, conversion of said mixture of acids into the methyl esters, fractional crystallization from a solvent consisting of a mixture of benzene and a low boiling petroleum ether, and recovery of the hydroxy-3-etiocholenic acid methyl ester from the first crystal fractions.

RUPERT OPPENAUER. CAREL CHRISTOF' BOLT. 

